Listener trace levels

Can anyone tell me what the different listener trace levels log to the trace file?

We need to change the IP of a listener, but it is thought that some of the applications may have IP addresses in the connections rather than hostnames.

What we intend to do is to add the new address to the listener configuration and change the dns server. we will leave it listening on both the old and new addresses for a period whilst we change what we can find, but it would be useful to be able to identify where a connection is coming in on the old address.